A gunman has shot dead a top member of the Afghan peace council in Kabul, striking another blow to efforts to negotiate a political resolution to the decade-long war.

Arsala Rahmani, a former Taliban official turned Afghan peace negotiator, was in his vehicle when he was killed by an unknown attacker at an intersection in the west part of the city, according to Mohammad Zahir, head of the Kabul police department's criminal investigation division.

The Taliban denied responsibility for the killing, although they had earlier indicated that they would target peace negotiators.

Rahmani was one of about 70 influential Afghans and former Taliban appointed by President Hamid Karzai to try to reconcile with the insurgents.

The US has backed the council's efforts to pull the Taliban into political discussions with Kabul as part of its strategy for reducing violence and turning over responsibility to Afghan forces, so international combat troops can go home or move into support roles by the end of 2014.

But this effort suffered a major setback in September 2011 when former Afghan president Burhanuddin Rabbani, who was head of the peace council, was assassinated by a suicide bomber posing as a peace emissary from the Taliban.

The US has its own contacts with the Taliban but in March the militant organisation said they were suspending contacts with Washington over what they said was a lack of progress in releasing prisoners from US detention in Guantánamo Bay.

The last substantive discussions between US officials and Taliban representatives were in January, and both initiatives to build trust and move toward real peace talks are in limbo.

On Twitter, the US embassy in Kabul called the assassination of another peace council member "a tragedy".

Rahmani served as minister of higher education during the Taliban regime, which ruled Afghanistan for five years and sheltered al-Qaida before being driven out of power in the US-led invasion in late 2001.

He reconciled with the government established in Kabul after the Taliban's fall and subsequently served in parliament.

Rahmani was one of several former members of the Taliban who were removed from a UN blacklist in July 2011. The decision by a UN committee eliminated a travel ban and an assets freeze against Rahmani and the others – a move seen as key to promoting the peace effort.

Taliban spokesman Zabiullah Mujahid said in a statement that his group had nothing to do with Rahmani's assassination.

When they announced the start of their annual "spring offensive" earlier this month, the Taliban said that members of the peace council who they view as government collaborators would be among their primary targets.

The offensive, which comes every year as the weather warms up, normally leads to an increase in attacks as the insurgents seek to intimidate the government and retake territory lost over the winter.